timer: rename NSEC_PER_SEC due to Mac OS X header clash
[qemu.git] / util / throttle.c
1 /*
2 * QEMU throttling infrastructure
3 *
4 * Copyright (C) Nodalink, EURL. 2013-2014
5 * Copyright (C) Igalia, S.L. 2015
6 *
7 * Authors:
8 * BenoƮt Canet <benoit.canet@nodalink.com>
9 * Alberto Garcia <berto@igalia.com>
10 *
11 * This program is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU General Public License as
13 * published by the Free Software Foundation; either version 2 or
14 * (at your option) version 3 of the License.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
20 *
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, see <http://www.gnu.org/licenses/>.
23 */
24
25 #include "qemu/throttle.h"
26 #include "qemu/timer.h"
27 #include "block/aio.h"
28
29 /* This function make a bucket leak
30 *
31 * @bkt: the bucket to make leak
32 * @delta_ns: the time delta
33 */
34 void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta_ns)
35 {
36 double leak;
37
38 /* compute how much to leak */
39 leak = (bkt->avg * (double) delta_ns) / NANOSECONDS_PER_SECOND;
40
41 /* make the bucket leak */
42 bkt->level = MAX(bkt->level - leak, 0);
43 }
44
45 /* Calculate the time delta since last leak and make proportionals leaks
46 *
47 * @now: the current timestamp in ns
48 */
49 static void throttle_do_leak(ThrottleState *ts, int64_t now)
50 {
51 /* compute the time elapsed since the last leak */
52 int64_t delta_ns = now - ts->previous_leak;
53 int i;
54
55 ts->previous_leak = now;
56
57 if (delta_ns <= 0) {
58 return;
59 }
60
61 /* make each bucket leak */
62 for (i = 0; i < BUCKETS_COUNT; i++) {
63 throttle_leak_bucket(&ts->cfg.buckets[i], delta_ns);
64 }
65 }
66
67 /* do the real job of computing the time to wait
68 *
69 * @limit: the throttling limit
70 * @extra: the number of operation to delay
71 * @ret: the time to wait in ns
72 */
73 static int64_t throttle_do_compute_wait(double limit, double extra)
74 {
75 double wait = extra * NANOSECONDS_PER_SECOND;
76 wait /= limit;
77 return wait;
78 }
79
80 /* This function compute the wait time in ns that a leaky bucket should trigger
81 *
82 * @bkt: the leaky bucket we operate on
83 * @ret: the resulting wait time in ns or 0 if the operation can go through
84 */
85 int64_t throttle_compute_wait(LeakyBucket *bkt)
86 {
87 double extra; /* the number of extra units blocking the io */
88
89 if (!bkt->avg) {
90 return 0;
91 }
92
93 extra = bkt->level - bkt->max;
94
95 if (extra <= 0) {
96 return 0;
97 }
98
99 return throttle_do_compute_wait(bkt->avg, extra);
100 }
101
102 /* This function compute the time that must be waited while this IO
103 *
104 * @is_write: true if the current IO is a write, false if it's a read
105 * @ret: time to wait
106 */
107 static int64_t throttle_compute_wait_for(ThrottleState *ts,
108 bool is_write)
109 {
110 BucketType to_check[2][4] = { {THROTTLE_BPS_TOTAL,
111 THROTTLE_OPS_TOTAL,
112 THROTTLE_BPS_READ,
113 THROTTLE_OPS_READ},
114 {THROTTLE_BPS_TOTAL,
115 THROTTLE_OPS_TOTAL,
116 THROTTLE_BPS_WRITE,
117 THROTTLE_OPS_WRITE}, };
118 int64_t wait, max_wait = 0;
119 int i;
120
121 for (i = 0; i < 4; i++) {
122 BucketType index = to_check[is_write][i];
123 wait = throttle_compute_wait(&ts->cfg.buckets[index]);
124 if (wait > max_wait) {
125 max_wait = wait;
126 }
127 }
128
129 return max_wait;
130 }
131
132 /* compute the timer for this type of operation
133 *
134 * @is_write: the type of operation
135 * @now: the current clock timestamp
136 * @next_timestamp: the resulting timer
137 * @ret: true if a timer must be set
138 */
139 bool throttle_compute_timer(ThrottleState *ts,
140 bool is_write,
141 int64_t now,
142 int64_t *next_timestamp)
143 {
144 int64_t wait;
145
146 /* leak proportionally to the time elapsed */
147 throttle_do_leak(ts, now);
148
149 /* compute the wait time if any */
150 wait = throttle_compute_wait_for(ts, is_write);
151
152 /* if the code must wait compute when the next timer should fire */
153 if (wait) {
154 *next_timestamp = now + wait;
155 return true;
156 }
157
158 /* else no need to wait at all */
159 *next_timestamp = now;
160 return false;
161 }
162
163 /* Add timers to event loop */
164 void throttle_timers_attach_aio_context(ThrottleTimers *tt,
165 AioContext *new_context)
166 {
167 tt->timers[0] = aio_timer_new(new_context, tt->clock_type, SCALE_NS,
168 tt->read_timer_cb, tt->timer_opaque);
169 tt->timers[1] = aio_timer_new(new_context, tt->clock_type, SCALE_NS,
170 tt->write_timer_cb, tt->timer_opaque);
171 }
172
173 /* To be called first on the ThrottleState */
174 void throttle_init(ThrottleState *ts)
175 {
176 memset(ts, 0, sizeof(ThrottleState));
177 }
178
179 /* To be called first on the ThrottleTimers */
180 void throttle_timers_init(ThrottleTimers *tt,
181 AioContext *aio_context,
182 QEMUClockType clock_type,
183 QEMUTimerCB *read_timer_cb,
184 QEMUTimerCB *write_timer_cb,
185 void *timer_opaque)
186 {
187 memset(tt, 0, sizeof(ThrottleTimers));
188
189 tt->clock_type = clock_type;
190 tt->read_timer_cb = read_timer_cb;
191 tt->write_timer_cb = write_timer_cb;
192 tt->timer_opaque = timer_opaque;
193 throttle_timers_attach_aio_context(tt, aio_context);
194 }
195
196 /* destroy a timer */
197 static void throttle_timer_destroy(QEMUTimer **timer)
198 {
199 assert(*timer != NULL);
200
201 timer_del(*timer);
202 timer_free(*timer);
203 *timer = NULL;
204 }
205
206 /* Remove timers from event loop */
207 void throttle_timers_detach_aio_context(ThrottleTimers *tt)
208 {
209 int i;
210
211 for (i = 0; i < 2; i++) {
212 throttle_timer_destroy(&tt->timers[i]);
213 }
214 }
215
216 /* To be called last on the ThrottleTimers */
217 void throttle_timers_destroy(ThrottleTimers *tt)
218 {
219 throttle_timers_detach_aio_context(tt);
220 }
221
222 /* is any throttling timer configured */
223 bool throttle_timers_are_initialized(ThrottleTimers *tt)
224 {
225 if (tt->timers[0]) {
226 return true;
227 }
228
229 return false;
230 }
231
232 /* Does any throttling must be done
233 *
234 * @cfg: the throttling configuration to inspect
235 * @ret: true if throttling must be done else false
236 */
237 bool throttle_enabled(ThrottleConfig *cfg)
238 {
239 int i;
240
241 for (i = 0; i < BUCKETS_COUNT; i++) {
242 if (cfg->buckets[i].avg > 0) {
243 return true;
244 }
245 }
246
247 return false;
248 }
249
250 /* return true if any two throttling parameters conflicts
251 *
252 * @cfg: the throttling configuration to inspect
253 * @ret: true if any conflict detected else false
254 */
255 bool throttle_conflicting(ThrottleConfig *cfg)
256 {
257 bool bps_flag, ops_flag;
258 bool bps_max_flag, ops_max_flag;
259
260 bps_flag = cfg->buckets[THROTTLE_BPS_TOTAL].avg &&
261 (cfg->buckets[THROTTLE_BPS_READ].avg ||
262 cfg->buckets[THROTTLE_BPS_WRITE].avg);
263
264 ops_flag = cfg->buckets[THROTTLE_OPS_TOTAL].avg &&
265 (cfg->buckets[THROTTLE_OPS_READ].avg ||
266 cfg->buckets[THROTTLE_OPS_WRITE].avg);
267
268 bps_max_flag = cfg->buckets[THROTTLE_BPS_TOTAL].max &&
269 (cfg->buckets[THROTTLE_BPS_READ].max ||
270 cfg->buckets[THROTTLE_BPS_WRITE].max);
271
272 ops_max_flag = cfg->buckets[THROTTLE_OPS_TOTAL].max &&
273 (cfg->buckets[THROTTLE_OPS_READ].max ||
274 cfg->buckets[THROTTLE_OPS_WRITE].max);
275
276 return bps_flag || ops_flag || bps_max_flag || ops_max_flag;
277 }
278
279 /* check if a throttling configuration is valid
280 * @cfg: the throttling configuration to inspect
281 * @ret: true if valid else false
282 */
283 bool throttle_is_valid(ThrottleConfig *cfg)
284 {
285 bool invalid = false;
286 int i;
287
288 for (i = 0; i < BUCKETS_COUNT; i++) {
289 if (cfg->buckets[i].avg < 0) {
290 invalid = true;
291 }
292 }
293
294 for (i = 0; i < BUCKETS_COUNT; i++) {
295 if (cfg->buckets[i].max < 0) {
296 invalid = true;
297 }
298 }
299
300 return !invalid;
301 }
302
303 /* fix bucket parameters */
304 static void throttle_fix_bucket(LeakyBucket *bkt)
305 {
306 double min;
307
308 /* zero bucket level */
309 bkt->level = 0;
310
311 /* The following is done to cope with the Linux CFQ block scheduler
312 * which regroup reads and writes by block of 100ms in the guest.
313 * When they are two process one making reads and one making writes cfq
314 * make a pattern looking like the following:
315 * WWWWWWWWWWWRRRRRRRRRRRRRRWWWWWWWWWWWWWwRRRRRRRRRRRRRRRRR
316 * Having a max burst value of 100ms of the average will help smooth the
317 * throttling
318 */
319 min = bkt->avg / 10;
320 if (bkt->avg && !bkt->max) {
321 bkt->max = min;
322 }
323 }
324
325 /* take care of canceling a timer */
326 static void throttle_cancel_timer(QEMUTimer *timer)
327 {
328 assert(timer != NULL);
329
330 timer_del(timer);
331 }
332
333 /* Used to configure the throttle
334 *
335 * @ts: the throttle state we are working on
336 * @tt: the throttle timers we use in this aio context
337 * @cfg: the config to set
338 */
339 void throttle_config(ThrottleState *ts,
340 ThrottleTimers *tt,
341 ThrottleConfig *cfg)
342 {
343 int i;
344
345 ts->cfg = *cfg;
346
347 for (i = 0; i < BUCKETS_COUNT; i++) {
348 throttle_fix_bucket(&ts->cfg.buckets[i]);
349 }
350
351 ts->previous_leak = qemu_clock_get_ns(tt->clock_type);
352
353 for (i = 0; i < 2; i++) {
354 throttle_cancel_timer(tt->timers[i]);
355 }
356 }
357
358 /* used to get config
359 *
360 * @ts: the throttle state we are working on
361 * @cfg: the config to write
362 */
363 void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg)
364 {
365 *cfg = ts->cfg;
366 }
367
368
369 /* Schedule the read or write timer if needed
370 *
371 * NOTE: this function is not unit tested due to it's usage of timer_mod
372 *
373 * @tt: the timers structure
374 * @is_write: the type of operation (read/write)
375 * @ret: true if the timer has been scheduled else false
376 */
377 bool throttle_schedule_timer(ThrottleState *ts,
378 ThrottleTimers *tt,
379 bool is_write)
380 {
381 int64_t now = qemu_clock_get_ns(tt->clock_type);
382 int64_t next_timestamp;
383 bool must_wait;
384
385 must_wait = throttle_compute_timer(ts,
386 is_write,
387 now,
388 &next_timestamp);
389
390 /* request not throttled */
391 if (!must_wait) {
392 return false;
393 }
394
395 /* request throttled and timer pending -> do nothing */
396 if (timer_pending(tt->timers[is_write])) {
397 return true;
398 }
399
400 /* request throttled and timer not pending -> arm timer */
401 timer_mod(tt->timers[is_write], next_timestamp);
402 return true;
403 }
404
405 /* do the accounting for this operation
406 *
407 * @is_write: the type of operation (read/write)
408 * @size: the size of the operation
409 */
410 void throttle_account(ThrottleState *ts, bool is_write, uint64_t size)
411 {
412 double units = 1.0;
413
414 /* if cfg.op_size is defined and smaller than size we compute unit count */
415 if (ts->cfg.op_size && size > ts->cfg.op_size) {
416 units = (double) size / ts->cfg.op_size;
417 }
418
419 ts->cfg.buckets[THROTTLE_BPS_TOTAL].level += size;
420 ts->cfg.buckets[THROTTLE_OPS_TOTAL].level += units;
421
422 if (is_write) {
423 ts->cfg.buckets[THROTTLE_BPS_WRITE].level += size;
424 ts->cfg.buckets[THROTTLE_OPS_WRITE].level += units;
425 } else {
426 ts->cfg.buckets[THROTTLE_BPS_READ].level += size;
427 ts->cfg.buckets[THROTTLE_OPS_READ].level += units;
428 }
429 }
430